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Kammoun A.,Computer | Couillet R.,University Paris - Sud | Pascal F.,University Paris - Sud | Alouini M.-S.,Computer
IEEE Transactions on Signal Processing | Year: 2016

This paper studies the behavior of regularized Tyler estimators (RTEs) of scatter matrices. The advantages of these estimators are twofold. First, they guarantee by construction a good conditioning of the estimate and second, being derivatives of robust Tyler estimators, they inherit their robustness properties, notably their resilience to outliers. Nevertheless, one major problem that poses the use of RTEs is represented by the question of setting the regularization parameter ρ. While a high value of ρ is likely to push all the eigenvalues away from zero, it comes at the cost of a larger bias with respect to the population covariance matrix. A deep understanding of the statistics of RTEs is essential to come up with appropriate choices for the regularization parameter. This is not an easy task and requires working under asymptotic regimes wherein the number of observations n and/or their size N increase together. First asymptotic results have recently been obtained when N and n are large and commensurable. Interestingly, no results concerning the regime of n going to infinity with N fixed exist. This motivates our work. In particular, we prove in this paper that the RTEs converge to a deterministic matrix when n → ∞ with N fixed, which is expressed as a function of the theoretical covariance matrix. We also derive the fluctuations of the RTEs around this limit and establish that these fluctuations converge in distribution to a multivariate Gaussian distribution with parameters depending on the population covariance and the regularization coefficient. © 2015 IEEE.

Rao A.,Computer | Ma H.,University of British Columbia | Alouini M.-S.,Computer | Chen Y.,University of Warwick
IEEE Transactions on Wireless Communications | Year: 2013

In a cognitive relay system, the secondary user is permitted to transmit data via a relay when licensed frequency bands are detected to be free. Previous studies mainly focus on reducing or limiting the interference of the secondary transmission to the primary users. On the other hand, however, the primary user traffic also affects the data transmission performance of the secondary users. In this paper, we mainly investigate the impact of the primary user traffic on the bit error rate (BER) of the secondary transmission, when the secondary user adopts adaptive transmission with a partially selected relay. In addition, the average collision time and the average collision probability have been used to measure the interference level caused by the secondary transmission to the primary users. Based on some selected numerical results, we can see that the primary user traffic seriously degrades the average BER. The worse-link partial selection can perform almost as well as the global selection when the channel conditions of the source-relay links and the relay-destination links are quite different. Although the relay selection improves the spectral efficiency of the secondary transmission, numerical results show that it only has slight impact on the overall average BER, which implies that the robustness of the system will not be affected by the relay selection. © 2002-2012 IEEE.

Ikki S.S.,Newcastle University | Ubaidulla P.,Computer | Aissa S.,University of Québec
IEEE Transactions on Wireless Communications | Year: 2014

In this paper, we investigate the effect of co-channel interference on the performance of cooperative diversity networks with amplify-and-forward (AF) relaying. We consider both conventional and opportunistic relaying. First, we obtain a tight upper-bound for the equivalent signal-to-interference-plus-noise ratio (SINR) at the destination. Subsequently, the cumulative distribution function (CDF), probability density function (PDF) and moment generating function (MGF) of the effective SINR are determined based on the upper-bound. Expressions for the error probabilities in both conventional and opportunistic relaying are derived utilizing the statistical characterization of the effective SINR. We also derive an approximate PDF of the equivalent instantaneous SINR at the destination. This leads to a simple and general asymptotic error probability expression which facilitates better insight into the effect of different system parameters on the error probability. Furthermore, we investigate the problem of optimum resource allocation in the network aiming at improving performance in the presence of resource constraints. We present numerical results that illustrate the excellent match between the analytical results and the simulation results, and the performance enhancement resulting from the proposed optimal resource allocation. © 2014 IEEE.

Lipor J.,Computer | Lipor J.,University of Michigan | Ahmed S.,Computer | Alouini M.-S.,Computer
IEEE Transactions on Signal Processing | Year: 2014

In multiple-input multiple-output (MIMO) radar settings, it is often desirable to transmit power only to a given location or set of locations defined by a beampattern. Transmit waveform design is a topic that has received much attention recently, involving synthesis of both the signal covariance matrix, R, as well as the actual waveforms. Current methods involve a two-step process of designing R via iterative solutions and then using R to generate waveforms that fulfill practical constraints such as having a constant-envelope or drawing from a finite alphabet. In this paper, a closed-form method to design R for a uniform linear array is proposed that utilizes the discrete Fourier transform (DFT) coefficients and Toeplitz matrices. The resulting covariance matrix fulfills the practical constraints such as positive semidefiniteness and the uniform elemental power constraint and provides performance similar to that of iterative methods, which require a much greater computation time. Next, a transmit architecture is presented that exploits the orthogonality of frequencies at discrete DFT values to transmit a sum of orthogonal signals from each antenna. The resulting waveforms provide a lower mean-square error than current methods at a much lower computational cost, and a simulated detection scenario demonstrates the performance advantages achieved. © 2014 IEEE.

Park K.-H.,Computer | Ko Y.-C.,Korea University | Alouini M.-S.,Computer
IEEE Transactions on Communications | Year: 2013

In this paper, we consider resource allocation method in the visible light communication. It is challenging to achieve high data rate due to the limited bandwidth of the optical sources. In order to increase the spectral efficiency, we design a suitable multiple-input multiple-output (MIMO) system utilizing spatial multiplexing based on singular value decomposition and adaptive modulation. More specifically, after explaining why the conventional allocation method in radio frequency MIMO channels cannot be applied directly to the optical intensity channels, we theoretically derive a power allocation method for an arbitrary number of transmit and receive antennas for optical wireless MIMO systems. Based on three key constraints: the nonnegativity of the intensity-modulated signal, the aggregate optical power budget, and the bit error rate requirement, we propose a novel method to allocate the optical power, the offset value, and the modulation size. Based on some selected simulation results, we show that our proposed allocation method gives a better spectral efficiency at the expense of an increased computational complexity in comparison to a simple method that allocates the optical power equally among all the data streams. © 2013 IEEE.

Tabassum H.,Computer | Yilmaz F.,Computer | Dawy Z.,American University of Beirut | Alouini M.-S.,Computer
IEEE Transactions on Wireless Communications | Year: 2013

This paper presents a novel framework for modeling the uplink intercell interference (ICI) in a multiuser cellular network. The proposed framework assists in quantifying the impact of various fading channel models and state-of-the-art scheduling schemes on the uplink ICI. Firstly, we derive a semi-analytical expression for the distribution of the location of the scheduled user in a given cell considering a wide range of scheduling schemes. Based on this, we derive the distribution and moment generating function (MGF) of the uplink ICI considering a single interfering cell. Consequently, we determine the MGF of the cumulative ICI observed from all interfering cells and derive explicit MGF expressions for three typical fading models. Finally, we utilize the obtained expressions to evaluate important network performance metrics such as the outage probability, ergodic capacity, and average fairness numerically. Monte-Carlo simulation results are provided to demonstrate the efficacy of the derived analytical expressions. © 2013 IEEE.

Alghadhban A.,Computer | Shihada B.,Computer
Proceedings of the NOMS 2016 - 2016 IEEE/IFIP Network Operations and Management Symposium | Year: 2016

Recent SDN researches suffer from over-accumulation of unhealthy flow-load. Instead, we leverage the SDN controller network view to encode the end-to-end path information into the packet address. Our solution EncPath significantly reduces the flow-table size and the number of control messages. Consequently, the power consumption of network switches is in orders of magnitude less than other evaluated solutions. It also provides flow management flexibility and scalability. We compare EncPath with single and multipath routing solutions and single path solution. Also, we operated them in proactive and reactive modes. We find that EncPath flow entries in core switches in a multihomed fat-tree with 144 hosts is approximately 1000 times smaller than Equal-Cost MultiPath (ECMP) and random routing. Additionally, the number of control messages to setup the network is reduced by a factor of 200×. This, consequently, affords data-plane and control-plane devices space to process other tasks. © 2016 IEEE.

Ahmed S.,Computer | Alouini M.-S.,Computer
IEEE Transactions on Signal Processing | Year: 2014

Compared to phased-array, multiple-input multiple-output (MIMO) radars provide more degrees-of-freedom (DOF) that can be exploited for improved spatial resolution, better parametric identifiability, lower sidelobe levels at the transmitter/receiver, and design variety of transmit beampatterns. The design of the transmit beampattern generally requires the waveforms to have arbitrary auto-and cross-correlation properties. The generation of such waveforms is a two-step complicated process. In the first step, a waveform covariance matrix is synthesized, which is a constrained optimization problem. In the second step, to realize this covariance matrix actual waveforms are designed, which is also a constrained optimization problem. Our proposed scheme converts this two-step constrained optimization problem into a one-step unconstrained optimization problem. In the proposed scheme, in contrast to synthesizing the covariance matrix for the desired beampattern, nT-independent finite-alphabet constant-envelope waveforms are generated and preprocessed, with weight matrix W, before transmitting from the antennas. In this work, two weight matrices are proposed that can be easily optimized for the desired symmetric and nonsymmetric beampatterns and guarantee equal average power transmission from each antenna. Simulation results validate our claims. © 2014 IEEE.

Garber L.,Computer
Computer | Year: 2012

As virtualization has become more popular, concern over the technology's security has grown. Traditional security techniques often don't work well with virtualization, so vendors are trying different approaches. © 2012 IEEE.

News Article | February 15, 2017

Community Care of North Carolina (CCNC) is facilitating a collaboration of health information technology (HIT) and pharmacy management vendors that aims to enhance the role community-based pharmacists play in providing integrated clinical services to patients. The effort will use existing standards adopted by medical providers in electronic medical records to develop an electronic pharmacy “care plan” – a shared document detailing a patient’s comprehensive medication use, health challenges and social care needs. The pilot will deploy across North Carolina pharmacies that are participating in the Community Pharmacy Enhanced Services Network (CPESNSM), a project supported by CCNC and the National Community Pharmacists Association. The Office of National Coordinator for Health Information Technology (ONC), encourages improved care coordination between pharmacists and other health care providers through various initiatives, grants, policies and regulations. For this effort, CCNC is a community based partner supporting ONC’s High Impact Pilot Award Recipient Lantana Consulting Group in implementing use of the electronic care plan among community pharmacists. The CPESN network will provide targeted services to an eligible population of greater than 3 million Medicaid, Medicare, and dually-eligible recipients. The project combines the efforts of five pharmacy management systems: Computer-Rx, PioneerRx, QS/1, RX30, VIP Pharmacy Systems and Creative Pharmacist as a clinical pharmacy intervention platform. This will allow pharmacy staff to document records in their own native system to simplify and streamline their workload while also documenting their role in population health management. Pharmacists will use the systems to share care plans electronically and improve care coordination. CCNC will receive the care plans and use electronic health record-ready, standardized data to assess quality of care and manage payment for enhanced services offerings. The move to an interoperable care plan linking pharmacists with other clinicians will reduce redundant data entry, make care plans more consistent in structure, and allow clinical information emanating from community pharmacies to be more easily exchanged with other members of the care team. The payment for enhanced services offerings are part of a 3-year cooperative agreement funded by the Centers for Medicare and Medicaid Innovation (CMMI) to test new reimbursement models for community pharmacies serving Medicaid, Medicare, dually eligible, and NC Health Choice beneficiaries. The project requires that participants assess project impact in three areas: practice efficiency, clinical quality, and interoperability. Troy Trygstad, VP of Pharmacy Programs for CCNC, reports that “We are thrilled to help accelerate Community-Based Pharmacy care coordination efforts by integrating their activities with the rest of the care team. As an organization focused on providing wrap-around support for primary care, we see high demand for efficient and effective exchange of care plans and associated information between pharmacies, practices, and other care team members. CPESN networks will greatly aid in that effort.” Shelly Spiro, Executive Director, Pharmacy Heath Information Technology (PHIT) Collaborative is pleased to assist CCNC and the pharmacy management system vendors with implementation of the Pharmacist eCare Plan standard project. This project meets the PHIT Collaborative’s mission of advocating and educating key stakeholders regarding the meaningful use of heath IT and the inclusion of pharmacists within a technology-enabled integrated health care system. The members of the PHIT Collaborative including the nine largest national pharmacy professional associations together with many significant related Associate Members support this effort. Tricia Lee Wilkins, Pharmacy Advisor and Health IT Specialist for ONC, states that “Pharmacists provide crucial services and clinical interventions necessary for optimizing patient health outcomes. For decades, the profession of pharmacy has pioneered use of information technology for medication management systems. It is exciting to see innovative pharmacists use health IT to support not only the documentation of clinical care but the exchange of that information as well.” The CCNC and the pharmacy management vendors are receiving implementation support from Lantana Consulting Group, the developer of the exchange specification, under a high-impact pilot cooperative agreement from the Office of the National Coordinator for Health IT. “We believe strongly in the power of efficient data standards to inform and improve care. This work inserts pharmacists into the information exchange economy and we are very pleased to support them in this effort,” says Zabrina Gonzaga, RN, manager of clinical analysis and policy at Lantana. About CCNC CCNC is the smart choice for physicians, providers and payers looking for ways to reduce costs and financial risks associated with managing high-cost, complex patients. The CCNC enterprise includes 14 community-based care management networks which serve all 100 North Carolina counties and work for more than 1600 contracted medical homes. CCNC is currently testing ways to integrate community pharmacists into the medical homes system and pioneering new methods of transforming medical practices to pay-for-value forms of provider reimbursement. In 2016, CCNC won the inaugural Hearst Health Award for excellence in improving population health. About Lantana Lantana Consulting Group is a leader in healthcare interoperability, strategy, and standards-based implementation. Lantana’s mission is to make health information available across the spectrum of care, supporting safe, effective, affordable healthcare that improves well-being, public health, quality of care, and research. ( About Computer-Rx Computer-Rx ( provides proven Pharmacy Management Software and Services that promote growth and efficiency in community pharmacy. We combine intuitive software features and the latest technology with a company culture that emphasizes customer service to partner with community pharmacies all over the U.S. to improve patient health. About PioneerRx Developed with the experience of over 35 years of pharmacy software development and support, PioneerRx was built from scratch to provide the pharmacy community with a solution that can grow as the industry changes for the next 35 years. PioneerRx delivers weekly improvements and cutting edge features that are designed to provide speed, simplicity, consistency, and flexibility; however, their goal of development is to help pharmacies make more money. PioneerRx leads the industry in first-to-market functionality in one seamlessly integrated package; they have become one of the most successful and frequently talked about pharmacy systems in the United States. About QS/1 QS/1 offers industry-leading healthcare software solutions to effectively manage independent, chain, hospital outpatient and long-term care pharmacies and HME businesses. QS/1’s complete software solutions are flexible and scalable, making them a valuable and affordable productivity tool for pharmacies – large or small. QS/1 is a division of the J M Smith Corporation, one of the largest privately-held companies in South Carolina. For additional information about QS/1 and the products and services it provides, visit or call 800.231.7776. About Rx30 Rx30 is a total Pharmacy Management Software application that truly acts as the hub for all pharmacy management activities, including prescription dispensing, fully automated refills and reminders, workflow management, medication therapy management and STAR ratings management. The Rx30 platform also excels at adherence management, medication synchronization, document management, smart phone/web refills, e-prescribing, POS, outbound customer communication, IVR integration, business reporting, label printing and a myriad of value added processes and interfaces that assist in streamlining pharmacy management activities and driving profit. For more information, please visit About VIP Pharmacy Systems: With over 30 years of serving independent pharmacies, VIP Pharmacy Systems is a leader in pharmacy management software, with a focus on speed, reliability, and quality customer care. The result of these efforts is that VIP provides one of the most comprehensive yet easy-to-use pharmacy management systems available. Email sales(at)vip-pharmacy(dot)com to learn how VIP can help you build a better pharmacy. About Creative Pharmacist Co-founded by a community pharmacist and a technology expert in 2008, Creative Pharmacist, developer of the STRAND® clinical platform, is the U.S. market leader in helping pharmacists launch clinical services within their community. They support community pharmacists across the country in engaging patients with chronic disease, such as diabetes, through STRAND®, a wide-reaching intervention, documentation, and education platform. Their mission is to transform the community pharmacy marketplace by inspiring and empowering pharmacists to engage clinical pharmacy practice to improve both the health of their business and the health of their patients. For more information, please visit:

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